One way in which tubular products have been conventionally produced from a substrate has been to wind the substrate helically with a rotating drive system incorporating a mandrel with a series of rollers. The rollers are set in bearings located in plates which support one end of the rollers. Each of the rollers is set at a predetermined angle to produce a forward helix in the manufactured tube formed by the substrate. The mandrel is driven by externally applied means, such as a belt drive or roller drive, which applies pressure to the substrate and one or more of the rollers to effect rotational and helical motion of the substrate. The tubular product is formed by adjacent windings of the substrate being wound in contact and fixed together by adhesive.
In order to manufacture tubular products of differing diameter or from substrates of different width, the rollers of the helix are required to be realigned to produce the correct helix. Re-aligning of the rollers is particularly time consuming as the angle relative to the backing plate must be carefully calculated and each of the rollers finely adjusted.
Mandrels of the above-described kind periodically require maintenance to replace the bearings in which the rollers are set. The bearings require replacement as the forces applied to the bearings from the belt or roller drive are large when compared to the size of the bearings, and cause the bearings to wear excessively.
It is an object of the present invention to provide one or more improvements in mandrels for manufacturing ducts and other tubular products.